Agricultural harvesters typically comprise a self-propelled combine with crop threshing, separating, or cleaning equipment, and a platform header attached to the front of the vehicle that the vehicle carries through the field. The harvesting platform cuts the crop by means of a sickle bar and conveys it to the center of the header using belt or auger conveyors.
The sickle bar comprises a number of knifes mounted on a support bar reciprocating in the lateral direction and driven by a transmission mounted on a lateral end of the header. The transmission is driven by a mechanical drive train from a feeder house of the combine. With increasing width of the headers, it became practicable to split the sickle bar into two separate halves, each driven from one end by a respective transmission (U.S. Pat. No. 3,577,716 A). The outputs of the transmissions are phase shifted by 180° in order to reduce the vibration induced by the sickle bar, such that the sickle bar halves move in opposite respective directions. It was also proposed to drive the two sickle bar halves from the center of the header by means of a transmission having two 180° phase shifted outputs (U.S. Pat. No. 5,497,605 A), or to drive a sickle bar half from one side and have a transmission at the center of the header providing the 180° phase shift for the other half of the sickle bar (U.S. Pat. No. 6,889,492 B). Another prior art proposal is to drive the sickle bar halves with separate hydraulic motors that are electronically synchronized to provide the phase offset (U.S. Pat. No. 7,658,059 B).
The proposal with the two transmissions requires a slip-free connection between the feeder house output and the transmissions in order to avoid a de-synchronization of the sickle bar halves. This requires use of rigid shafts which are relatively heavy and can only be implemented with expensive telescopic shafts in case that the platform is extendable, i.e. comprises a rear part releasably connected to the feeder house and a front part that can be extended forward with respect to the rear part, in order to adapt the platform for harvesting special crops, like rape. The central drive requires drive train elements connected to the feeder house output beneath the platform, where only limited space is available. The proposal with the phase shifting transmission requires a relatively large and thus expensive transmission sufficient to drive the entire sickle bar, while the hydrostatic drive is complex and expensive.
It is thus an object of the present invention to provide a drive assembly for an agricultural harvesting platform that avoids or reduces the mentioned disadvantages.